Technical Abstract:
Pectolytic enzymes are especially important for fruit and vegetable juice technology. Common uses include clarification, pulp treatment, tissue maceration, liquefaction and other specialty functions. A common component of commercial pectinases is endo-polygalacturonase (EPG). Seven different forms of EPG have been identified from Aspergillus niger, a common fungal source. Two different modes of action, processive and non-processive, have been identified for A. niger EPGs on substrates having a degree of polymerization (DP) of eight or fewer. Their mode of action on substrates with a larger DP, like those present in demethylated pectin and undigested polygalacturonic acid (PGA), has not been determined. We have used two commercial monocomponent EPG preparations, one of which has been identified as EPG I by MALDI-TOF MS, and compared their digestion patterns. We also compared their mode of action on size fractionated PGAs with a DP range from 1-9, 9-20 and 23-40. For partially digested PGA our results show that the two PGAs have different modes of action. During the first 30 minutes of digestion one appears to preferentially accumulate fragments in a DP range of 3-7 while the other accumulates fragments in broader DP range from 4-22. After 300 minutes the first EPG still accumulated fragments in the 3-8 range and the second appeared to have a possible bi-modal distribution with a major peak at DP 5-12 and a second at DP 12-18. These results suggest that functional properties of the resulting GA oligomers could be manipulated by the choice of EPG isozymes used for tissue treatment.